Wang Yubo, Ren Meibin, Wang Yifan, Wang Lu, Liu Hong, Shi Mei, Zhong Yaohua
State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, 266237, China.
School of Medicine, Henan Polytechnic University, Jiaozuo, Henan 454003, China.
Eng Microbiol. 2022 Nov 15;3(1):100059. doi: 10.1016/j.engmic.2022.100059. eCollection 2023 Mar.
Cellulose degradation results from the synergistic effect of different enzymes, but which enzyme is involved in the initial stage of cellulose degradation is still not well understood. Cellobiohydrolase 2 (CBH2) attached to the conidial surface is possibly associated with the initial stage. However, its specific mechanism is still incompletely known. This study explored the potential role of CBH2 in initiating cellulose degradation using a constitutive overexpression strategy. First, the CBH2-overexpression strains Qgc2-5 and Qrc2-40 were constructed using the constitutive promoters P and P, respectively. It was found that was expressed at a high level under the glucose conditions and was significantly higher than that of the parental strain QM9414 at the early stage of 29 h when cellulose was used as the carbon source. Particularly, the constitutive overexpression of caused the strong expression of major cellulase-encoding genes (, and ) and the rapid decomposition of cellulosic material. Meanwhile, the scanning electron microscope showed that the groove-like structure of the cellulose surface was eroded seriously owing to CBH2 overexpression, which caused the cellulose surface to be smooth. These results showed that the overexpression of CHB2 caused the major cellulase enzymes to be expressed and contributed to cellulose degradation, showing the potential role of CBH2 in the initial stage of the cellulose hydrolytic process.
纤维素降解是由不同酶的协同作用导致的，但参与纤维素降解初始阶段的是哪种酶仍未完全清楚。附着在分生孢子表面的纤维二糖水解酶2（CBH2）可能与初始阶段有关。然而，其具体机制仍不完全清楚。本研究采用组成型过表达策略探讨了CBH2在启动纤维素降解中的潜在作用。首先，分别使用组成型启动子P构建了CBH2过表达菌株Qgc2-5和Qrc2-（此处原文似乎有误，可能是Qrc2-40）。发现（此处原文似乎有误，可能是CBH2）在葡萄糖条件下高水平表达，并且在以纤维素为碳源的29小时早期显著高于亲本菌株QM9414。特别地，（此处原文似乎有误，可能是CBH2）的组成型过表达导致主要纤维素酶编码基因（此处原文似乎有误，可能是相关基因名称未完整给出）的强烈表达和纤维素材料的快速分解。同时，扫描电子显微镜显示，由于CBH2过表达，纤维素表面的沟状结构被严重侵蚀，导致纤维素表面变得光滑。这些结果表明，CHB2（此处原文似乎有误，应该是CBH2）的过表达导致主要纤维素酶的表达并促进了纤维素降解，显示了CBH2在纤维素水解过程初始阶段的潜在作用。
